In the general- and accent-lighting applications, customers often require flexibility in the angular distribution of the light. This flexibility is sometimes related to the lighting being used in a space that has changing requirements. An example is a retail space where different products are displayed in different ways each week. In this retail space example, spot lights may be desirable for small items, and wider beam flood lights might be appropriate for larger items.
Another common situation is where a lighting designer or architect will place light points within a space before the final furniture or decoration design is set. The furniture and decoration become targets for the lighting to illuminate once they are set in place, and they may require specific light beam spreads to achieve desirable lighting.
The lighting consumer has several options to install adjustable light today. For very large fixtures used in factories or warehouses, there are often one or two settings for a socket within a large reflector. By moving the socket, a customer can change the beam spread to a few different settings, but this is rarely done because of the difficulty involved. Instead, the fixtures are usually set in the factory and never changed.
A second option available today is to use lamps with integral reflectors that have different beam spreads. One example of this is low voltage halogen lamps, of which MR-16 is a common type. The MR-16 lamps are available in several light beam spreads from very narrow spot lights (with angular extents of about 7 degrees) to very wide flood lights (with angular extents of about 60 degrees). The most common beam spreads for the accent-lighting applications where MR-16s are used are 15, 25 and 40 degrees. This strategy causes complications when lamps are changed after burning out. All MR-16s are very similar in appearance, and beam patterns within a space are only maintained after re-lamping if the exact same lamp is used to replace the burned out lamp. This strategy also requires many different lamp types to be kept on hand.
Fiber optic lighting has historically offered an easier option for adjusting beam spread. Because fiber optic lighting delivers lighting in a forward direction of usually less than about one steradian, it can easily be controlled with imaging or non imaging lenses. By moving the fiber output face with relation to the beam forming lens, different beam spreads can be achieved. Fiber optic lighting fixtures exist today which allow infinite adjustment of the distance from the lens to the fiber. Sometimes these fixtures will have visual guides to help the installer guide the beam setting to the desired angular setting. Because there is infinite adjustment, and only a visual guide to beam setting, in any field of fixtures that are desired to be at the same beam angle, significant variation will be observed. So, the beam-angle accuracy is limited to the skill of the installer. Further, these types of infinite-adjustable systems often rely on compression on the fiber with a set screw or compression fitting to hold the fiber in place. When the angular distribution of the light is changed frequently, these mechanical stresses on the fiber will cause damage leading to further beam inconsistency and light loss.
It would thus be desirable to provide a light pipe fixture that allows easy adjustment of beam spreads of the light, even after the fixture has been installed.
It would further be desirable to provide a light pipe fixture in which mechanical stresses imposed on the light pipe supplying light to the fixture is minimized.